Fourth generation (4G) mobile communications systems aim at achieving high data rates at relatively low costs. Throughput of 1 Gbps at local area or 10 Mbps for wide area result in high spectral efficiencies. Physical limitations due to higher propagation losses incurred at the higher carrier frequencies to be used in 4G systems result in smaller cell areas. Therefore, efficient resource allocation is crucial in achieving the targeted throughput while controlling the cost.
Bit loading and, in general, controlling the relevant transmission parameters are key methods for approaching the capacity limits, and thereby using the spectral resources efficiently. All bit and power allocation schemes require a measure of the mutual information during a time interval of interest, or some approximation thereof.
In the currently used systems, it is assumed that the channel state information in complex form is known or can be predicted. The complex form, with both magnitude and phase, permits calculation of the exact eigenvalues or singular values. However, if the frame (time interval where relevant transmission parameters are to be adapted) is long and the time-varying nature of the channel is pronounced, the adaptation based on the calculated eigenvalues or singular values becomes less reliable.
Thus, it is desirable and advantageous to provide a method for transmission parameters selection that is not dependent upon the singular value decomposition, or on the exact calculation of eigenmodes, eigenvalues or singular values.